Proppant from captured carbon

ABSTRACT

Method of making and using a proppant from captured carbon in either a carbon mineralization process or in a carbon nanomaterial manufacturing process is discussed, followed by treatments to ensure the quality control of the proppants so that they are suitable for use in hydraulic and other reservoir fracturing methods.

PRIOR RELATED APPLICATIONS

This application is a DIVISIONAL application of U.S. Ser. No.17/736,087, entitled PROPPANT FROM CAPTURED CARBON, filed May 3, 2022,which claims priority to U.S. Ser. No. 63/201,662, entitled PROPPANTFROM CAPTURED CARBON, filed May 7, 2021. Each is incorporated byreference in its entirety for all purposes.

FEDERALLY SPONSORED RESEARCH STATEMENT

Not applicable.

FIELD OF THE DISCLOSURE

The disclosure generally relates to methods, products and systems forfracturing shale formations and thereby sequestering carbon.

BACKGROUND OF THE DISCLOSURE

In many formations, chemical and/or physical processes alter thereservoir rock over geologic time. Sometimes, these diagenetic processesrestrict the openings in the rock and reduce the ability of fluids toflow through the rock. If fluids cannot flow, it is difficult to produceoil, gas or water from a well. Thus, low permeability reservoirs areoften fractured to increase their permeability and thereby increase theproduction of fluids.

Hydraulic fracturing is the process of pumping fluid into a wellbore atan injection rate that is too high for the formation to accept withoutbreaking rock. During injection, the resistance to flow in the formationincreases and the pressure in the wellbore increases to a value calledthe break-down pressure, that is the sum of the in situ compressivestress and the strength of the formation. Once the formation “breaksdown,” a fracture is formed, and injected fluid can then flow through itto the wellbore for production.

During a fracking job, a fluid not containing any solid (called the“pad”) is injected first, until the fracture is wide enough to accept apropping agent. A fluid plus propping agent is injected next. Thepurpose of the propping agent is to keep apart the fracture surfacesonce the pumping operation ceases (see e.g., FIG. 1 ). Frequently thefrack fluids contain a gel to help carry the proppant deep into thereservoir.

Sand and ceramic proppant are two major types of proppants applied inthe field. Comparing to the sand, ceramic proppant has higher hardnessand sphericity, both ensure a large fracture conductivity especially athigh effective closure stress. However, it is also moreexpensive—typically 3-5 times more expensive than sands (See FIG. 2 ).In deep reservoirs, man-made ceramic beads are used to hold open or“prop” the fracture, but in shallower reservoirs sand is typically used.

Although sand is inexpensive and an adequate propping agent for manyfracking needs, it would be extremely beneficial to the planet as awhole if we could sequester carbon in some manner downhole, thusreturning the carbon to the ground from which we have liberated it inthe form of oil and natural gas. In 2016, hydraulically fracturedhorizontal wells accounted for 69% of all oil and natural gas wellsdrilled in the United States and 83% of the total linear footagedrilled. Thus, any method that combines fracking and carbonsequestration has the potential to be transformational and significantlycombat increasing CO₂ levels, especially where a given frack job usesmillions of pounds of proppant.

SUMMARY OF THE DISCLOSURE

The disclosure is a novel propping agent made from captured carbon, andmethods of making and using this novel propping agent.

Chemically, it is known that carbon dioxide may be sequestered bymineral carbonation. In carbon mineralization, CO₂ reacts with mineralsrich in Ca and Mg to form carbonates, such as calcite (CaCO₃), magnesite(MgCO₃), and dolomite (CaMg(CO₃)₂), and often quartz (SiO₂). Someidealized reactions are as follows:

wollastonite CaSiO₃+CO₂→CaCO₃olivine Mg₂SiO₄+2CO₂→2MgCO₃+SiO₂pyroxenes CaMgSi₂O₆+2CO₂→CaMg(CO₃)₂+2SiO₂serpent polytypes Mg₃Si₂O₅(OH)₄+3CO₂→3MgCO₃+2SiO₂+2H₂Obrucite Mg(OH)₂+CO₂→MgCO₃+H₂O

Although, mineral carbonation is known, and many are pursuing costeffective and efficient means of performing these reactions at scale,the issue of how to dispose of the product remains. Most proposals callfor the production of various construction materials, and use ofmineralization for concrete production, both to cure cement and toproduce aggregate, is already economically viable in some cases. Seee.g., Carbon8 System Ltd (UK), with a modular carbon capture system thatproduces >150,000 tonnes of product per year.

We propose using the carbonated mineral as a frac sand or proppant,rather than as building materials. The potential sequestration could beenormous, since as much as 0.3-13 million pounds of sand can be used tofracture a well and nearly 70 percent of all producing wells in theUnited States, including the vast majority of new wells, arehydraulically fractured. Indeed, some 120 million tons of frac sand wereused in 2020 in the US and the usage is projected to continue to grow.

Indeed, companies are already making carbon capture carbonate aggregatesfor the construction industry, in sizes ranging from sand sized togravel sized. Blue Planet, for example, uses recycled concrete in itsremediation process as a means of obtaining calcium and alkalinity. CO₂from flue gas is converted to carbonate by contacting CO₂ containing gaswith a water-based capture solutions. See FIG. 4 . The captured CO₂ doesnot require a purification step—an energy and capital intensive process.Thus, the method costs less than traditional methods of CO₂ capture. Afacility is planned with capacity of 70,000 tons per year of coatedlightweight aggregate and up to 500,000 tons per year of remediatedrecycled concrete aggregates (coarse and fine). Although still in thepilot stage, Chevron has invested 10 million dollars in this start-up.

A second option is to make a proppant from carbon nanomaterials (CNM),such as carbon nanofibers or carbon nanotubes. Many groups are makingcarbon products, but scalability on the order required may still presentissues. There was only 161,200 metric tonnes (355 million pounds) ofglobal carbon fiber capacity in 2019—an amount that is far short of whatis needed on the fracking industry. However, carbon nanomaterials havethe advantage that they can easily be made into a variety of shapes bymolding and vacuum forming and their global capacity increases everyyear.

In addition, CNM, such as carbon nanofibers, carbon nanotubes, andgraphene, are known to have extraordinary properties, such as havinghigh strength and low weight. Thus, the making of proppants of specificsize, shape and density is technically feasible and scalability willcontinue to improve over time.

Bergen Carbon Solutions, for example, has a modular process thatincludes the use of CO₂ from carbon capture facilities or CO₂ emissiondirectly from factory chimneys as feedstock in CNM production. See FIG.5 and FIG. 6 . An electrolysis/heat process breaks the chemical bondingand pure carbon (C) can then be taken out of the production module andtransferred to the filtration module which separates aggregates. In thisinstance, the filtration module may not be necessary, depending on thesize of proppant needed. Remnant CO₂ is recycled back to the chimneysystem and oxygen (O₂) is emitted through a vented duct in theproduction module or sent back to the factory chimney system. Theelectricity needed for the CNM production is only 50 kWh per kg CNM andthe capacity for a single module is 6.5 tonnes of CNM per year. Incomparison, traditional CNM production methods require 1400 kWh per kgCNM on average.

In either case, the proppant should meet basic proppant requirements andtypical ranges for some qualities are shown in Table 1 below. Thequality control of the proppants is to be determined under ISO 13503-2(1), incorporated by reference in its entirety for all purposes.

The carbon captured proppant should be sufficiently hard to meet itspurpose. The crush resistance test is performed by crushing a sample ofproppants under increasing stress. The highest stress level (roundeddown to the nearest 1000 psi) under which the proppants generate no morethan 10% crushed material is defined as the crush resistance (sometimescalled the K-value). Higher the crush resistance is, better theproppants are. The crushing rate of ceramic proppants under a stress of52 MPa is 5%, while the sands under a stress of 28 MPa is 9%, and thecarbon capture proppants should at least meet the 9% at 28 MPa standardof sand, and a 5% rate or better would be even more preferred.

The carbon capture proppant should also be available in the requiredparticle sizes. Size affects fracture conductivity and proppanttransport and is measured in mesh size ranges defined by the number ofopenings across one linear inch of screen. Smaller the mesh size numberis, larger the particle size is. Larger proppants provide higherfracture conductivity because the pore spaces present in the proppantpack are larger. However, larger proppants may crush more easily becausethere are fewer contact points or smaller contact areas to distributethe stress applied to the proppant pack. Also, larger proppants are moredifficult to transport through the fracture, as they tend to settle outquickly unless there is sufficient porosity.

The range of particle sizes also affects the permeability/conductivityof a proppant pack, although particles can be size sorted so the methodneed not manufacture a narrow range of sizes. A wider range of particlesizes results in a tighter packing arrangement and lowerpermeability/conductivity. For example, 40/60-mesh proppants (a range of20 mesh) will provide better permeability/conductivity than 40/70-meshproppants (a range of 30 mesh).

Typical proppant sizes are generally between 8 and 140 mesh (106 μm-2.36mm), for example 16-30 mesh (600 μm-1180 μm), 20-40 mesh (420 μm-840μm), 30-50 mesh (300 μm-600 μm), 40-70 mesh (212 μm-420 μm) or 70-140mesh (106 μm-212 μm). When it comes to determining if a frack sand meetsaccepted specs, at least 90% of the frack sand must fall within themarketed mesh size.

In addition, it would be a benefit, if not essential, if shape could becontrolled. Proppant particle shape is measured by its sphericity androundness. Sphericity is defined as the ratio of the surface area of asphere to the surface area of the particle. The sphericity is 1 for asphere and is less than 1 for any particle that is not a sphere.Roundness defines how smooth a grain is, and can be definedmathematically as the ratio of the average radius of curvature of theedges or corners to the radius of curvature of the maximum inscribedsphere.

FIG. 3 shows a visual chart that can be used for evaluating thesphericity and roundness of proppant grains. Ceramics typically achievethe roundness and sphericity of 0.9, while sands are typically in the0.7 range, with some occasionally at 0.8. Proppant particles of highersphericity and roundness will lead to greater conductivity. Highersphericity and roundness also improve the crush resistance of theproppants.

Density affects proppant transport and is another important parameter.Proppant density comes with both bulk density and absolute density. Thedifference between the bulk and absolute densities results from the voidspaces present in proppant packs. Bulk density includes both theproppant and the porosity and is measured by filling a known volume withdry proppant and measuring the weight. Apparent density excludesextra-granular porosity by placing a known mass in a volume of fluid anddetermining how much of the fluid is displaced (Archimedes). Absolutedensity is the density the material would have if no intra-granularporosity is present.

Typical porosity values of proppant packs are in the range between 0.35and 0.43%. For natural sands, the absolute density usually rangesbetween 2.62 and 2.65 in specific gravity as compared to quartzdominated sane. For ceramic proppants, the absolute density usuallyranges between 2.55 and 3.9 in specific gravity. The carbon captureproppants should be in this range, and it may be possible to change thedensity with coatings or by influencing void spaces/porosity.

Turbidity is a measure of clays, silts and other fine particulatespresent in the proppants. It is measured by a turbidity meter that looksat light refraction in water exposed to the proppants. The presence ofclays and silts reduces conductivity. Turbidity can be removed bywashing, so the presence of some fines in manufacturing is notproblematic.

Acid solubility determines the percentage of acid soluble materialspresent in the proppants. Lower acid solubility indicates a smalleramount of “impurities” present in the proppants. These twospecifications are generally provided by proppant suppliers for eachtype of proppants, but are more relevant for evaluating natural sandsfor fracturing applications. Calcium carbonate proppants would likelynot be combined with acid etching or other acid treatments as they areexpected to be acid soluble, thus this test may be omitted for thismineral.

Flowback of a proppant following fracture stimulation treatment is amajor concern because of the damage to equipment caused by particulatesentering equipment and potential loss in well production as wells aretaken offline for repair. Coating proppants with a polymer can reduceflowback. Thermoplastic film materials, adhesive coated fibers, apoly(urethane) coating that slowly polymerizes after the fracturingtreatment due to a polyaddition process and magnetic materials have allbeen developed to reduce the proppant flowback.

The carbon capture method can be carbon mineralization or carbonnanomaterial synthesis, using any method known in the art or to bedeveloped, potentially followed by any processes needed to controlproppant quality, such as washing, size sorting, coating, and the like.

The fracturing method can be any suitable methods or combinations ofmethods. Thus, the method could employ aspects of hydraulic fracking,thermal fracking, cryogenic fracking, electric fracking, explosivefracking, pneumatic fracking and the like.

Any preflush and afterflush procedures can be combined with the method.For example, preflush may be used to clean the rock and/or increasewettability. Afterflush may be used to clear out gels and otherpolymers.

Any suitable fracturing fluid can be used, although water-based frackfluids are likely to be preferred, probably with polymers to increaseviscosity for proppant mobility. A number of fluids are described Table2 below.

Corrosion inhibitors, demulsifiers, surface tension reducing agents,chemical retarding agents, clay stabilizers, friction reducers and otheradditives referred to above may be incorporated in the fracturing fluidif desired. Care should again be taken that the additives selected arecompatible with the other components, as well as with the carrier fluid.Some commonly used additives are described below:

Surfactants: Surfactants are used to reduce surface and interfacialtension, to prevent emulsions, to water wet the formation, and tosafeguard against other associated problems. Swabbing and clean-up timecan be reduced by lowering surface tension.

Suspending Agents: Agents to suspend fines. Suspension should bedifferentiated from dispersion. Dispersed particles usually settle in ashort time.

Sequestering Agents: Sequestering agents act to complex ions of iron andother metallic salts to inhibit precipitation of iron. Sequesteringagents should always be used if rusty tubing or casing is to becontacted.

Anti-Sludge Agents: Some crudes, particularly heavy asphaltic crudes,form an insoluble sludge when contacted with acid. The primaryingredients of a sludge are usually asphaltenes, but sludges may alsocontain resins and paraffin waxes, high-molecular weight hydrocarbons,and formation fines or clays. Addition of certain surfactants canprevent sludge formation by keeping colloidal material dispersed.

Corrosion Inhibitors: Corrosion inhibitors temporarily slow down thereaction of acid on metal. Corrosion inhibition time varies withtemperature, acid concentration, type of steel, and inhibitorconcentration. Both organic and inorganic corrosion inhibitors haveapplication in acidizing. Some organic inhibitors are effective up tothe 300° F. (148.8° C.) range. Extenders have been developed to increasethe effective range to 400° F. (204.4° C.). Inorganic arsenic inhibitorcan be used up to at least 450° F. (232.2° C.).

Alcohol: Normally methyl or isopropyl alcohol in concentrations of 5% to30% by volume can be used to lower surface tension. The use of alcoholin acid will accelerate the rate of well clean-up and improve clean-up,particularly in dry gas wells. Disadvantages are increased inhibitorproblems and possible salt precipitation.

Fluid Loss Control Agents: Fluid loss control agents may be required toreduce leak-off, particularly in fracture acidizing. The preferredmethod of selecting fluid loss control agents is to run fluid loss testson cores from the formation to be fracked.

Diverting or Bridging Agents: Fluids will usually follow the path ofleast resistance, usually the lesser damaged intervals, unless divertingor bridging agents are employed to allow relatively uniform treatment ofvarious porous zones open to the wellbore.

The invention includes the following one or more embodiments, in anycombination thereof:

A method of making a proppant for use in hydraulic fracturing of a well,said method comprising: a) capturing CO₂ from a gas or a liquid; b)reacting said CO₂ with magnesium or calcium ions in a carbonmineralization reaction under alkaline pH to make porous particles ofmagnesium carbonate or calcium carbonate; c) said particles having: i) acrushing rate of <10% at 28 MPa, ii) a bulk density of about 1.5-2.5g/cm³, iii) a size of about 0.1-2 mm, and iv) a porosity of about30-50%; d) size sorting said particles to produce size ranges of between20 mesh (e.g. 40-60 mesh range) and 40 mesh (e.g., a 20-60 mesh range),said size sorted particles being suitable for use as a proppant.

A method of making a proppant for use in hydraulic fracturing of a well,said method comprising: a) capturing CO₂ from a gas or a liquid; b)reacting said CO₂ with electricity or heat or both to produce carbonnanomaterial (CNM); c) optional sonication and/or filtration of saidCNM; d) optional shaping said carbon nanomaterial by vacuum forming ormolding or agglomeration; e) said CMN having: i) a crushing rate of <10%at 28 MPa, ii) a bulk density of 1.5-2.5 g/cm³, iii) a size of 0.1-2 mm,and iv) a porosity of 30-50%; f) size sorting said CMN to produce sizeranges of between 20 mesh (e.g. 40-60 mesh range) and 40 mesh (e.g., a20-60 mesh range), said size sorted CNM being suitable for use as aproppant.

Any CNM proppant or CNM manufacturing method herein described, said heatbeing about 800° C.

A proppant made by any method herein described.

A method of producing oil or gas from an underground formation having atleast one well, comprising the method steps of: a) introducing a firstfracturing fluid (FF) through the at least one well into the undergroundformation at a pressure greater than a minimum in-situ rock stress forformation of fractures (FR) in the underground formation; b) introducinga second FF containing any proppant herein described through the atleast one well into the underground formation to prop open said FR; andc) producing oil or gas from said at least one well.

Any proppant or method herein described, said particles further having aroundness of at least 0.7 and a sphericity of at least 0.7.

Any proppant or method herein described, said further comprising coatingsaid particles with a resin, a thermoplastic polymer or an adhesivepolymer.

Any proppant or method herein described, said further comprisingcombining said proppant with magnetic particles or with fibers.

Any proppant or method herein described, said particles having acrushing rate of <9% at 28 MPa, or <8, <7, <6 or <5 MPa or having acrushing rate of <10% at 40 MPa or at 50 MPa.

Any proppant or method herein described, said where said particles areagglomerated to produce sizes larger than 100 nm, 500 nm, 1 mm or 1.5mm.

Any proppant or method herein described, said where said particles areagglomerated and coated to produce sizes larger than 100 nm, 500 nm, 1mm or 1.5 mm.

Any proppant or method herein described, said, where CO₂ is capturedfrom a flue gas stream and said magnesium or calcium ions are fromrecycled cement, brine or mining tailings.

A “fracture” is a crack, delamination, surface breakage, separation orother destruction within a geologic formation or fraction of formationnot related to foliation or cleavage in metamorphic formation, alongwhich there has been displacement or movement relative to an adjacentportion of the formation. A fracture along which there has been lateraldisplacement may be termed a fault. When walls of a fracture have movedonly normal to each other, the fracture may be termed a joint. Fracturesmay enhance permeability of rocks greatly by connecting pores together,and for that reason, joints and faults may be induced mechanically insome reservoirs in order to increase fluid flow. Fractures may benatural or man-made.

A “transverse fracture” is a fracture that is more than 15 degreesdeviated from the axis of the well bore, and is usually roughlyperpendicular thereto. A “longitudinal” or “axial” fracture is oriented15 degrees or less from the axis of the wellbore, e.g., substantiallyparallel to the wellbore.

A “hydraulic fracture” is a fracture at least partially propagated intoa formation, wherein the fracture is created through injection ofpressurized fluids into the formation. While the term “hydraulicfracture” is used, the techniques described herein are not limited touse in hydraulic fractures. The techniques may be suitable for use inany fractures created in any manner considered suitable by one skilledin the art. Hydraulic fractures may be substantially horizontal inorientation, substantially vertical in orientation, or oriented alongany other plane. Generally, the fractures tend to be vertical at greaterdepths, due to the increased mass of the overburden.

As used herein, “hydraulic fracturing” is a process used to createfractures that extend from the wellbore into formations to stimulate thepotential for production. A fracturing fluid, typically viscous, isgenerally injected into the formation with sufficient pressure, forexample, at a pressure greater than the lithostatic pressure of theformation, to create and extend a fracture. A proppant may often be usedto “prop” or hold open the created fracture after the hydraulic pressureused to generate the fracture has been released. Parameters that may beuseful for controlling the fracturing process include the pressure ofthe hydraulic fluid, the viscosity of the hydraulic fluid, the mass flowrate of the hydraulic fluid, the amount of proppant, and the like.

The use of the word “a” or “an” when used in conjunction with the term“comprising” in the claims or the specification means one or more thanone, unless the context dictates otherwise.

The term “about” means the stated value plus or minus the margin oferror of measurement or plus or minus 10% if no method of measurement isindicated.

The use of the term “or” in the claims is used to mean “and/or” unlessexplicitly indicated to refer to alternatives only or if thealternatives are mutually exclusive.

The terms “comprise”, “have”, “include” and “contain” (and theirvariants) are open-ended linking verbs and allow the addition of otherelements when used in a claim.

The phrase “consisting of” is closed, and excludes all additionalelements.

The phrase “consisting essentially of” excludes additional materialelements, but allows the inclusions of non-material elements that do notsubstantially change the nature of the invention, such as additives,preflush fluids or steps, afterflush fluids or steps, and the like. Thetransition phrases “comprise,” “consisting of” and “consistingessentially of” in the claims are intended to be interchangeable, but inthe interests of brevity the claims are not repeated three times hereinwith the three variations.

The following abbreviations are used herein:

ABBREVIATION TERM Frack Short for fracture, see also fracking FrackingRefers to fracturing a reservoir, e.g., inducing fracture formation. CNMCarbon nanomaterials, including CNM that have been treated by molding,pressure, and the like to reach mm size. FF Fracturing fluid FRFractures MPa Megapascal

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 Schematic of hydraulic fracturing of a natural gas reservoir.

FIG. 2 Exemplary sand and ceramic proppants.

FIG. 3 . Sphericity and roundness.

FIG. 4 Blue Planet carbon capture and mineralization process.

FIG. 5 Bergen Carbon Solutions carbon capture and manufacture of CNMprocess.

FIG. 6 Closeup of reactor in FIG. 5 .

DETAILED DESCRIPTION

The disclosure provides a novel proppant, method of making same, andmethods of using same in hydraulic and other types of fracturing of oil,gas, and water wells.

The examples herein are intended to be illustrative only, and not undulylimit the scope of the appended claims.

Carbon Mineralization

In one embodiment, particulates are made by contacting a gaseous sourceof CO₂ (such as flue gas or CO₂ from a direct air capture (DAC) system)and an aqueous capture ammonia to produce a solid carbonate product andan aqueous ammonium salt, and then contacting the aqueous ammonium saltliquid with a geomass, e.g., alkaline waste product such as recycledcement, to regenerate the aqueous capture ammonia.

In some embodiments, combination of the CO₂ capture liquid and gaseoussource of CO₂ results in production of an aqueous carbonate, whichaqueous carbonate is then subsequently contacted with a divalent cationsource, e.g., a Ca²⁺ and/or Mg²⁺ source, to produce the CO₂ sequesteringmaterial. In yet other embodiments, a one-step CO₂ gas absorptioncarbonate precipitation protocol is employed.

Any convenient cation source may be employed in such instances. Cationsources of interest include, but are not limited to, the brine fromwater processing facilities such as sea water desalination plants,brackish water desalination plants, groundwater recovery facilities,wastewater facilities, blowdown water from facilities with coolingtowers, produced water and the like, which produce a concentrated streamof solution high in cation content. Also of interest as cation sourcesare naturally occurring sources, such as but not limited to nativeseawater and geological brines. In some instances, the cation source maybe a waste product of another step of the process, e.g., a calcium salt(such as CaCl₂) produced during regeneration of ammonia from the aqueousammonium salt.

In yet other embodiments, the aqueous capture ammonia includes cations,e.g., as described above. The cations may be provided in the aqueouscapture ammonia using any convenient protocol. In some instances, thecations present in the aqueous capture ammonia are derived from ageomass used in regeneration of the aqueous capture ammonia from anaqueous ammonium salt. In addition, and/or alternatively, the cationsmay be provided by combining an aqueous capture ammonia with a cationsource, e.g., as described above.

The gaseous source of CO₂ can be waste streams produced by industrialplants that combust fossil fuels, e.g., coal, oil, natural gas, as wellas man-made fuel products of naturally occurring organic fuel deposits,such as but not limited to tar sands, heavy oil, oil shale, etc. Incertain embodiments, power plants are pulverized coal power plants,supercritical coal power plants, mass burn coal power plants, fluidizedbed coal power plants, gas or oil-fired boiler and steam turbine powerplants, gas or oil-fired boiler simple cycle gas turbine power plants,and gas or oil-fired boiler combined cycle gas turbine power plants.Direct capture from air may also be used.

Geomass can be mine tailings, mining dust, sand, baghouse fines, soildust, dust, cement kiln dust, slag, steel slag, iron slag, boiler slag,coal combustion residue, ash, fly ash, slurry, lime slurry, lime, kilndust, kiln fines, residue, bauxite residue, demolished concrete,returned concrete, crushed concrete, recycled concrete, recycled mortar,recycled cement, demolished building materials, recycled buildingmaterials, recycled aggregate, etc.

Carbon Nanomaterials

Carbon dioxide is electrochemically decomposed to carbon and oxygen gasin molten LiCl-5.0 wt. % Li₂O molten salts at 903 K (629.8° C.) using atitanium cathode and inert platinum anode (Li 2016). CO₂ chemicallydissolves into the LiCl—Li₂O melt by reacting with Li₂O, changing theelectrolyte LiCl—Li₂O—CO₂ into Li₂CO₃ and LiCl. Carbonate anions areelectrochemically reduced to carbon on the cathode, while oxygencomplexes of carbonate anions are oxidized at the anode, generating O₂.Electrolysis of the LiCl-5.0 wt. % Li₂O molten salt under a CO₂atmosphere at 0.05 A/cm² in Li (2015) yielded anodic gas with a CO₂/O₂ratio of 0.42. The CO₂/O₂ ratio increased with increasing currentdensity.

CO₂ can also be dissolved into carbonates and electrochemically split toproduce CNM. Carbon deposition in CaCO₃, SrCO₃ and BaCO₃ dissolvedelectrolyte occurs and carbon products aggregate on the cathodicsurface, and then collected. Li (2018) demonstrated that the alkalineearth carbonate additives sustained continuous CO₂ electrolysis andcarbon electro-deposition. However, the micromorphology andmicrostructure of the carbon deposits were found to be significantlychanged mainly because of the interface modification induced by thealkaline earth carbonate additives. However, such changes may notpresent problems for proppant use, plus higher yields may be obtained byoptimizing the electrolytic conditions. Compared to pure Li₂CO₃,alkaline earth carbonate additives provide the carbon nanotubes with athicker diameter and more prominent hollow structure.

Tables

TABLE 1 Properties of 20/40 ceramic proppants and sands. Type ofproppants Ceramic Sand Mesh range (mesh) 20/40 20/40 Bulk density(g/cm³) 1.58 1.59 Apparent density (g/cm³) 2.84 2.63 Average diameter(μm) 617 658.3 Turbidity (FTU) 14 37 Roundness (dimensionless) 0.8 0.7Sphericity (dimensionless) 0.8 0.7 Acid-solubility (%) 6.9 7 Crushingrate (%) 5 (effective closure 9 (effective closure stress = 52 MPastress = 28 MPa

TABLE 2 Frack Fluids Base Fluid Fluid Type Main Composition Water basedSlickwater Water + sand (+chemical additives which may includesurfactant, friction reducer, scale inhibitor, and biocide) Linearfluids Gelled water, GUAR < HPG, HEC, CMHPG Cross-linked fluidCrosslinker + GUAR, HPG, CMHPG, CMHEC Viscoelastic surfactant gelElectrolite + surfactant fluids Foam based Water based foam Water andFoamer + N₂ or CO₂ Acid based foam Acid and Foamer + N₂ Alcohol basedfoam Methanol and Foamer + N₂ Oil based Linear fluids Oil, Gelled OilCross-linked fluid Phosphate Ester Gels Water Emulsion Water + Oil +Emulsifiers Acid based Linear — Cross-linked — Oil Emulsion — Alcoholbased Methanol/water mixes or Methanol + water 100% methanol Emulsionbased Water-oil emulsions Water + Oil CO₂-methanol CO₂ + water +methanol Others — Other fluids Liquid CO²⁻ CO₂ Liquid nitrogen N₂ Liquidhelium He Liquid natural gas LPG (butane and/or propane)

The following references are incorporated by reference in their entiretyfor all purposes.

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1. A method of making a proppant for use in hydraulic fracturing of awell, said method comprising: a) capturing CO₂ from a gas or a liquid;b) reacting said captured CO₂ with electricity or heat or both toproduce carbon nanomaterial (CNM); c) optional sonication and/orfiltration of said CNM; d) optional shaping said CNM by vacuum formingor molding or agglomeration; e) said CMN having: (1) a crushing rate of<10% at 28 MPa, (2) a bulk density of 1.5-2.5 g/cm³, (3) a size of 0.1-2mm, and (4) a porosity of 30-50%; f) size sorting said CMN to produce asize range of 20 mesh range or a size range of 40 mesh range, said sizesorted CNM being suitable for use as a proppant.
 2. The method of claim1, where CO₂ is captured from a flue gas stream or from air.
 3. Themethod of claim 1, said heat being about 800° C.
 4. The method of claim1, said CNM further having a roundness of at least 0.7 and a sphericityof at least 0.7.
 5. The method of claim 1, further comprising coatingsaid CNM with a resin, a thermoplastic polymer or an adhesive polymer.6. The method of claim 1, further comprising combining said proppantwith magnetic particles.
 7. The method of claim 1, said CNM having acrushing rate of <10% at 40 MPa.
 8. The method of claim 1, where saidparticles are agglomerated to produce sizes larger than 100 nm.
 9. Themethod of claim 1, where said particles are agglomerated and coated toproduce sizes larger than 100 nm.
 10. A method of making a proppant foruse in hydraulic fracturing of a well, said method comprising: a)capturing CO₂ from air or a flue gas stream; b) reacting said capturedCO₂ with electricity or heat or both to produce carbon nanomaterial(CNM); c) optional sonication and/or filtration of said CNM; d) optionalshaping said CNM by vacuum forming or molding or agglomeration; e) saidCMN having: (1) a crushing rate of <10% at 28 MPa, (2) a bulk density of1.5-2.5 g/cm³, (3) a size of 0.1-2 mm, and (4) a porosity of 30-50%; f)size sorting said CMN to produce a proppant having a size range between20 mesh range or 40 mesh range.
 11. The method of claim 10, said heatbeing about 800° C.
 12. The method of claim 10, said CNM further havinga roundness of at least 0.7 and a sphericity of at least 0.7.
 13. Themethod of claim 10, further comprising coating said CNM with a resin, athermoplastic polymer or an adhesive polymer.
 14. The method of claim10, further comprising combining said proppant with magnetic particles.15. The method of claim 10, said CNM having a crushing rate of <10% at40 MPa.
 16. The method of claim 10, where said particles areagglomerated to produce sizes larger than 100 nm.
 17. The method ofclaim 10, where said particles are agglomerated and coated to producesizes larger than 100 nm.
 18. A proppant made by the method of claim10-17.
 19. A method of producing oil or gas from an undergroundformation having at least one well, comprising the method steps of: a)introducing a first fracturing fluid (FF) through said at least one wellinto the underground formation at a pressure greater than a minimumin-situ rock stress for formation of fractures (FR) in the undergroundformation; b) introducing a second FF containing the proppant of claim18 through said at least one well into the underground formation to propopen said FR; and c) producing oil or gas from said at least one well.